The determination (e.g., detection or concentration measurement) of an analyte in a fluid sample is of particular interest in the medical field. For example, it can be desirable to determine glucose, ketone bodies, cholesterol, lipoproteins, triglycerides, acetaminophen or glycosylated hemoglobin (HbA1c) concentrations in a sample of a bodily fluid such as urine, blood, plasma or interstitial fluid. Such determinations can be achieved using an analytical test strip and test meter combination. For example, a diabetic patient conventionally tests his or her blood glucose using an analytical test meter and a disposable test strip. The user inserts the disposable test strip into the analytical test meter, then applies a drop of his or her blood to a sample-receiving chamber on the test strip. The analytical test meter applies test electrical signals to the blood in the sample-receiving chamber via electrodes and conductors on the test strip, and monitors resulting electrical signals. A processor in the analytical test meter can then determine the user's blood glucose (e.g., in mg glucose per dL of blood, or mmol glucose per L of blood) using the resulting electrical signals.
However, various factors can confound or interfere with such determinations. For example, U.S. Pat. No. 7,390,667 to Burke et al. describes that reagents in the sample-receiving chamber are used to provide charge carriers that are not otherwise present in blood. Consequently, the electrochemical response of the blood in the presence of a given signal is intended to be primarily dependent upon the concentration of blood glucose. Secondarily, however, the electrochemical response of the blood to a given signal is dependent upon other factors, including temperature and hematocrit (HCT), the percentage by volume of red blood cells in the blood.
U.S. Pat. No. 8,343,331 to Choi describes a method of correcting erroneous measurement results in a biosensor. A first voltage is applied to a blood sample on a test strip and a hematocrit value of the blood sample is calculated using a measured electric current value. A second voltage is then applied, and a glucose level is calculated using a second measured electric current value. The glucose level is corrected by using the calculated hematocrit value. However, this requires an accurate measurement of hematocrit to provide results of a desired accuracy.
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